Fetal loss of a twin during first
trimester is not an uncommon event [1]. Loss of one twin in the first
trimester does not appear to impair the development of the surviving
twin. However, fetal death occurring after midgestation (17 weeks' gestation) may increase the risk of IUGR, preterm labor, preeclampsia and perinatal mortality [2,3].
Consequently, serial assessments of fetal growth and well-being should
be considered.

Maternal coagulopathy following twin demise appears to be uncommon [3, 4].
However, coagulopathy has been reported to occur up to 3 weeks
following fetal demise [5]. Therefore, when fetal demise occurs in
multiple gestation after the first trimester an initial maternal
clotting profile with reassessment in two to three weeks is not
unreasonable. Monitoring of maternal coagulation factors is not
necessary when fetal loss occurs prior to 13 weeks' gestation [12].

When fetal demise occurs after midgestation there is a 17% chance that the "surviving twin" in a monochorionic gestation will either die or suffer major morbidity [6]. Morbidity and mortality approach 50% when twin-to twin transfusion is present [7]. Major morbidity is unlikely to occur in the surviving twin of a dichorionic gestation [6, 8].
Antenatal necrosis of the cerebral white matter has been associated with the presence of intrauterine fetal death of a co-twin , artery-to-artery, and vein-to-vein anastomosis. However, vein-to-vein anastomosis has the strongest association with antenatal necrosis of the cerebral white matter in affected twin pregnancies [9].
DNA zygosity studies may be used to assess the risk to the normal twin in the event of the co-twin's demise [10].

Prompt delivery following the death of a co-twin has not been shown to prevent preexisting neurological injury or injury that occurred at the time of the co-twin’s death. Delivery for the purpose of preventing injury should, therefore, be weighed against the risks of premature delivery. [11].
In known monozygotic twins with impending death preterm delivery may be
considered to prevent neurological injury. However, the risks of
neurological injury should be weighed against the risks associated with
premature delivery.